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Old August 12th 03, 06:48 PM
Richard Clark
 
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On 12 Aug 2003 11:23:27 GMT, oSaddam (Yuri Blanarovich)
wrote:

Question to Roy,
can EZNEC model loading coils in loaded antennas, like mobile whips including
the physical properties of the coil?
I just had some exchange with W8JI on eHam.net
http://www.eham.net/articles/5998
where he is ignoring the fact that loading coil is part of the radiator and its
physical properties, where length to diameter ratio have impact on the current
distribution in the coil.
He is claiming that modeling programs confirm his statement that the current is
the same at the both ends of the loading coil (close in short coils) . I am
having hard time to see how the modeling program is capturing physical
properties of the coil besides inductance, Q etc.
W9UCW has done considerable amount of work on the subject and has measured that
the current diminishes in the loading coil away from the feedpoint.

Thanks!

Yuri, K3BU


Hi Yuri,

When I open the load dialog window, it presents R in some form or
another (the answer to your Q provision). Are you concerned the
program will treat the load as an infinitesimally small object? If it
does, you could decimate the coil inductance and distribute it across
10 segments whose span is equivalent to your anticipated physical
length. Perhaps a lot of trouble (and perhaps there's another, better
way), but it seems to be the price of your query.

73's
Richard Clark, KB7QHC
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Old August 13th 03, 01:32 AM
Yuri Blanarovich
 
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When I open the load dialog window, it presents R in some form or
another (the answer to your Q provision). Are you concerned the
program will treat the load as an infinitesimally small object? If it
does, you could decimate the coil inductance and distribute it across
10 segments whose span is equivalent to your anticipated physical
length. Perhaps a lot of trouble (and perhaps there's another, better
way), but it seems to be the price of your query.

73's
Richard Clark, KB7QHC


That sounds reasonable.
Including physical properties of the coil (Length/diameter ratio, physical
size) in the calculations of the model could help to optimize the system, allow
more precise calculations and participation in the optimization routines.
If the load is treated as point, the current is considered the same at the
entrance and exit of the coil, which is not the case especially in longer
loading coils. Question is to what extent is program capable of capturing and
then massaging it and what is the correlation to real life situations.
I got some RF ammeters, it will be interesting to see wasaaap.

Yuri, K3BUm
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